Integrated circuits are typically formed on a semiconductor substrate, such as a silicon wafer or other semiconducting material. In general, layers of various materials which are either semiconducting, conducting or insulating are utilized to form the integrated circuits. By way of example, the various materials are doped, ion implanted, deposited, etched, grown, etc. using various processes. Further, a continuing goal in semiconductor processing is to continue to strive to reduce the size of individual electronic components, thereby enabling smaller and denser integrated circuitry.
One technique for patterning and processing semiconductor substrates is photolithography. Such typically includes deposition of a photoresist layer which can be processed to modify the solubility of such layer in certain solvents. For example, portions of the photoresist layer can be exposed through a mask/reticle to change the solvent solubility of the exposed regions versus the unexposed regions compared to the as-deposited state. Thereafter, the exposed or unexposed portions can be removed, depending on the type of photoresist, thereby leaving a masking pattern of the photoresist on the substrate. Adjacent areas of the substrate next to the masked portions can be processed, for example by etching or ion implanting, to effect the desired processing of the substrate adjacent the masking material.
In certain instances, multiple different layers of photoresist are utilized in a given masking/photolithographic step. Further, the photolithographic masking and patterning might be combined with one or more other layers. One such process forms what is commonly referred to as a “hard mask” over the substrate prior to deposition of the photoresist layer or layers. The photoresist layer is then patterned, for example as described above, to form masking blocks over the hard mask. The hard mask is then etched using the photoresist as a mask to transfer the pattern of the photoresist of the hard mask. The photoresist may or may not be removed immediately thereafter. Hard masks such as just described provide a more robust masking pattern than photoresist alone, for example should the photoresist be completely eroded/etched away.
One material utilized as a hard mask is amorphous carbon. The amorphous carbon might be doped with other materials, for example boron. When etching oxide material using an amorphous carbon as a hard mask, the etching typically removes the oxide at a rate of about ten times faster than it removes amorphous carbon.
In many instances, it is desirable to use an antireflective coating (with or without a hard mask) over which the photoresist is deposited. In the absence of an antireflective coating, some underlying substrates reflect a considerable amount of the incident radiation which can adversely affect the patterning of the photoresist. Accordingly even when using amorphous carbon hard mask patterning, an antireflective coating might be employed intermediate the amorphous carbon and the photoresist layer. The antireflective coating might be composed of a single layer, or multiple layers. For example, one antireflective coating might be inorganic, and another antireflective coating might be organic. For example in one implementation, an antireflective coating over amorphous carbon comprises a first inorganic layer and a second organic layer. Photoresist is deposited thereafter and, after photolighographic exposure and developing, openings are formed through the photoresist to the antireflective layer(s). The mask pattern in the photoresist layer is then typically transferred through the antireflective layer(s), and through the amorphous carbon layer, utilizing one or more dry anisotropic etching techniques. Then, one or more suitable different chemistries are typically utilized to extend the openings through the layer or layers inwardly of the amorphous carbon layer.
In typical photolithographic processing, depositing of the photoresist tends to form what is referred to as an “edge bead” which constitutes an excessive, thickened section of resist at the peripheral outer edge of the wafer or substrate. The edge bead can be several times as thick as the layer of resist which is more centrally received over the substrate. This can, in some instances, leave an edge bead of resist over the antireflective coating and over amorphous carbon in a peripheral region about the edge of the substrate after the mask pattern has been formed in the amorphous carbon layer. Such photoresist in the peripheral region and/or any antireflective coating can cause residual amorphous carbon and antireflective coating to remain on the substrate/wafer edge after dry etching and cleaning. Such can subsequently peel away later, and undesirably cause particle contamination.
The invention was motivated in addressing and improving upon the above-described issues. However, it is in no way so limited. The invention is only limited by the accompanying claims as literally worded (without interpretative or other limiting reference to the above background art description, remaining portions of the specification or the drawings), and in accordance with the doctrine of equivalents.